Pressed paper plates are typically formed from flat blanks. The blanks may be scored around their perimeter to aid in the necessary gathering of the paper during the formation of the product. The folds or pleats created in the final pressware product ideally are pressed and reformed with heat, moisture and pressure to “rebond” the structure and obtain high strength. A preferred apparatus for making paperboard pressware is a heated, segmented die set including a punch and die of the class seen in, for example, U.S. patent application Ser. No. 11/465,694, Publication No. US 2007/0042072 of Johns et al., referred to above. In a typical construction of such die sets, the pressure and draw rings are spring mounted and include cylindrical guide pins to maintain relative position including rotational registration between the outer pressure and draw rings with their respective punch and die base members.
Wearing of the guide pins and their bushings is a problem, as is binding of the pins if too much rotation or twist occurs. The binding problem is particularly exacerbated by relatively significant clearances needed to accommodate thermal expansion of the parts; which expansion largely occurs in a radial direction. The prior art system using pins and bushings does not provide substantial support to the die set segments angularly offset with respect to the machine direction, further aggravating wear issues with the parts as the outer rings bear upon the inner members of the die set during inclined operation. As the die set wears and clearances between parts increases, MD and angular alignment during forming strokes becomes even more problematical and breakage of springs occurs, resulting in downtime and expense.